Regulatory T cells are increased in tuberculosis patients and closely correlate with its immunopathology

Objective To determine whether regulatory T cells(Tr)are increased in patients with tuberculosis and whether they are associated with its immunopathology.Meantime,to investigate the possibility of tuberculosis(TB)as a model for studying Tr functions.Methods The lymphocyte subsets were isolated from peripheral blood mononuclear cells by sorting with flow cytometry.Total cellular RNA was extracted and RT-PCR was performed to detect the Foxp3 mRNA in purified CD3+CIM+T cells,CD3+CD8+T cells and non-CD3+CD4+CD8+T cells.Using FACS analysis.we further investigated the distribution of Foxp3+ population in CD4+ CD25+T cells.Finally,we compared the percentage of CD4+CD25highFoxp3+T cells present in 51 active patients with tuberculosis and 40 uninfected healthy control subjects by FACS.The detection of Tr infiltration of Foxp3+ cells were performed with immunohistochemistry(IHC)method on tuberculosis pathological sections.Results Foxp3 was specific expressed in CD3+CD4+T cells,either in tuberculosis patients or healthy control subjects.Foxp3+ T cells took about 85%fraction of CD4+ CD25highpopulation.We used CD4+CD25high Foxp3+as a detective markers for Tr in the FACS analysis.The results showed that patients with active TB had a 4.4 fold higher percentage within the CD4+T cells in peripheral blood compared to healthy control group(modian,1.01%vs 0.23%,P<0.01).Much higher frequency of Tr were found along with T cells infiltration at the tuberculosis pathological tissues.A few individuals that we can followed indicated the expanded Tr was declined after curative treatment with operation.Conclusion Tr cells are increased in tuberculosis patients and closely correlate with its immunopathology.Tuberculosis should be a valuable model for Tr functional study. Key words: Natural regulatory T cell; CD4+CD25highFoxp3+; Tuberculosis; Immunopathology